Most people who spend time around the marine environment know that many species of fish are attracted to structures and hard surfaces in the ocean. Imagine tropical fish flocking to coral reefs, salmon hiding out under piers, and fish attracted to navigation buoys. The question has been posed as to whether fish will be attracted to marine energy devices placed in the ocean as well. And if they are attracted, could tidal and wave devices pose a threat to these fish or their prey?
H. T. Harvey & Associates addressed this question in a 2015 report in which they evaluated the potential ecological interactions with wave and tidal devices in the waters of the US west coast and Hawai‘i. Foundations and anchors to hold tidal and wave energy systems on the seabed may function as artificial reefs that attract reef-associated fishes, while the midwater and surface structures, such as mooring lines, buoys, and wave or tidal energy devices, may function as fish aggregating devices (FADs). As there are few marine renewable energy devices in the water in the US, the research team focused on surrogate devices such as artificial and natural reefs, oil and gas platforms, kelp beds, marine debris, buoys used to enhance fishing opportunities, aquaculture net pens, piers, and docks.
The researchers surmised that the portions of marine renewable energy systems placed on or near the seabed in coastal waters of the U.S. West Coast and Hawai‘i likely will function as small-scale artificial reefs and attract potentially high densities of reef-associated fishes (including fish that are protected under the Endangered Species Act such as certain species of rockfish along the west coast). The midwater and surface structures of wave devices placed in the tropical waters of Hawai‘i will likely function as FADs, attracting different species of fish, depending on the water depth and distance to shore. Fewer fish are expected to be attracted to the midwater and surface structures of wave devices along the west coast, although some juvenile rockfishes that live in kelp forests may congregate temporarily on devices in coastal waters from southern California to Washington. Other fish that visit the coastline occasionally or seasonally, such as jack mackerel, may also be associated with wave devices.
The study examined whether the congregation of fish around seafloor installations or mid/surface water devices is likely to cause harm to the fish, and concluded that increased predation or other effects on important coastal fish such as juvenile salmonids or rockfish is unlikely. In addition, the study found that wave devices installed off southern California have the potential to attract fish, and perhaps increase the productivity of rockfish in the area.
While there is still limited information to definitively evaluate effects of aggregating fish around marine renewable energy devices, there have been no specific mechanisms of harm identified that would lead to injury or death of fish from the presence of the devices.